This invention relates to a device for securing electrolysis cell membranes and more specifically, to a device which holds electrolysis cell membranes securely in place during the membrane's installation and removal from an electrolytic cell.
Electrolytic cells utilizing a membrane member are well known. There are also many well-known membranes for use in such electrolytic cells. For example, typical membranes include the perfluorinated carboxylic or sulfonic cation exchange membranes such as Nafion.RTM. manufactured by E. I. duPont de Nemours and Company or Flemion.RTM. manufactured by Asahi Glass Company, Ltd. These membranes are typically available in sheet form and employed in filter press-type or flat plate-type electrolytic cells having monopolar or bipolar electrodes.
Examples of bipolar, filter press-type cells are described in U.S. Pat. Nos. 4,111,779 and 4,108,742. These cells are used, for example, to carry out electrolysis of an aqueous alkali metal halide to produce a halogen, for example chlorine, and an alkali metal hydroxide such as sodium hydroxide. Generally, the bipolar, filter press-type electrolytic cell is composed of several bipolar unit cells arranged in series. One bipolar unit cell has an anode and cathode compartment separated by a partition wall. Typically, the anode and cathode are attached to opposite sides of the partition wall. The membrane is usually interposed between two adjacent unit cells to separate the anode compartment from the cathode compartment. A plurality of anode and cathode frames are installed in a parallel fashion and a longitudinal compressive, usually by a clamping means, is applied to the anode and cathode frames with the membrane inter posed between the frames to form the electrolytic cell completely.
During assembly of filter press type electrolytic cells, the membrane, interposed between an anode and cathode compartment, is held between the frames manually by personnel until squeezed. During disassembly of the cells, the membrane, again, must be held between the frames manually or it may fall between the frames and crease or wrinkle. The creasing or wrinkling of the membrane may cause the membrane to fail due to breaks or tearing during its use.
U.S. Pat. No. 4,170,535 discloses a membrane securing device which can be used to retain membranes in electrolytic cells during assembly and disassembly of the cell. The device in U.S. Pat. No. 4,170,535 comprises a non-conducting semi-rigid slotted tube which rests on the upper portion of the cell frame. The tube is at least one inch, preferably at least two inches in diameter. The upper edge of the membrane is stapled or otherwise attached to a plastic strip. The thickness of the strip is greater than the width of the slot so that the membrane with a strip attached to the top edge can be inserted into the slot and retained in the tube.
The disadvantage of the device in U.S. Pat. No. 4,170,535 is that no attachment device is provided to attach the top edge of the membrane to the plastic strip. Stapling the membrane to the strip as taught in the patent will not allow one to remove the plastic strip from the membrane without damaging the membrane. Leaving the plastic strip with the membrane on top of the cell frame will be possible only if there is enough spacing between the nozzles and lifting lugs or between the lifting lugs of the two adjacent cells. Otherwise, the plastic strip will have to stay above the nozzles and the lifting lugs. This arrangement also will be possible only if the membrane is wide enough to have more area hanging out on top of the cell.
Another disadvantage of the device disclosed in U.S. Pat. No. 4,170,535 is that the plastic strip with limited dimensions might not be rigid enough to hold a large size membrane flat without creasing or wrinkling it. Furthermore, the slotted tube which is used to retain the plastic strip inside and which is at least 1 inch, or preferably 2 inches in diameter, also can interfere with the nozzles and the lifting lugs on the top of the cell frame if the membrane is not wide enough to allow the tube to rest on top of the nozzles or lifting lugs.
It is therefore desired to provide a novel membrane hanging device which does not have the problems of the prior art.